1. Field of the Invention
This invention relates to telecommunications systems, especially PBX/Server systems, also referred to as Multi-Line Telephone Systems (MLTS). Specifically, the invention relates to completing an emergency, e.g. 911, call from a station/device behind a MLTS to a public network emergency facility and delivering precise location information of the caller based on a port equipment number associated with the port from which the emergency call originated.
2. Brief Description of the Prior Art
When a caller calls an emergency number, e.g. 911, the call is routed to a Public Safety Answering Point (PSAP). In some jurisdictions, regulatory agencies require that the caller's telephone number/callback number and/or precise physical location referred to as Location Identification Number (ELIN), be automatically provided to the PSAP. This information is used to locate the caller and to call back to the caller should there be a disconnect.
A caller identification (i.e., telephone number and ELIN) may be delivered to the PSAP either in-band (e.g., using DTMF signaling) or out-of-band (e.g., using ISDN signaling) depending on the type of trunk circuit employed. For residential callers Caller ID number is sufficient for the PSAP. For PBX/server service many users, e.g., commercial callers, hotel guests; an ELIN is required for this complex environment, for example, street address, floor number, room number, desk number. In some cases, the ELIN is geodetic, i.e. includes earth coordinates or GPS data.
Modern PBX/MLTS systems provide many new features to accommodate the way modern businesses operate. For example, employees may be assigned personal identification numbers (PINs) that are used by the PBX/MLTS to identify the employee and assign a telephone number to him/her. Further, for example, if an employee is assigned to a different location in the building, an automatic relocation feature can be activated using the PIN to reassign the employee's telephone number to the new location.
Another feature of PBX/MLTS systems is that some telephones connected to the PBX/MLTS system may not be provided with the ability to receive direct (inward) dialed calls. For example, in a hotel, telephones in rooms are typically not capable of receiving a direct inward call from outside the hotel, therefore they have no known Caller ID to identify them to the PSAP. no known Caller ID to identify them to the PSAP.
Still another feature of modern PBX/MLTS systems is that it is possible to make many or even all telephone lines available for use by multiline devices connected to the system. Thus, a caller from behind the PBX/MLTS system may be identified by many different telephone numbers.
All of these features of modern PBX/MLTS systems present problems for transmitting call back number and ELIN to a PSAP in an emergency call. In many situations, the only callback number provided from the PBX/MLTS system is the main directory billing number. In situations where the caller has utilized the automatic relocation feature of the PBX/MLTS system, the caller will be identified by employee PIN but not by a specific location. In situations where the caller has no direct inward call receive capability, the PSAP cannot call back the caller in the event of a disconnect. In the situation of a call from a multiline device, the telephone number from which the emergency call is made may not be the primary number for the caller and a return call to that number may cause a different device to ring rather than the caller's device. Moreover, the number used by the emergency caller may be associated with a ELIN which is not the caller's ELIN.